1. Field of the Invention
This invention relates broadly in the field of electronic musical tone generators and in particular is concerned with provision for automatically varying the tone envelope modulation with changes in playing speed.
2. Description of the Prior Art
Keyboard operated electronic musical instruments tend to produce mechanical-like tonal responses which are very unlike those produced by skilled musicians playing conventional acoustic orchestral musical instruments. Various systems have been proposed and implemented whose object is to reduce the characteristic mechanical-like precision of tone generation that is produced by the basic simple form of a keyboard operated electronic musical instrument.
Touch response systems have been used to make the loudness of a tone proportional to the speed with which a keyboard switch has been actuated. A typical touch response system is described in U.S. Pat. No. 4,121,490 entitled "Touch Responsive Electronic Piano."
Keyboard switches have been constructed to provide signals for controlling electronic musical effects such as tremolo and glide. In U.S. Pat. No. 3,835,235 entitled "Keyboard Type Electronic Musical Instrument" a photo electric arrangement is described for sensing the left-right motion of the keyboard switch as distinct from the up-down motion used in the conventional fashion to control tone generators. The left-right motion sensor output is used to provide the control signal to generate a glide or a portamento effect. In this fashion the magnitude of the effect is sensitive to the musician's individual touch on a particular key.
Systems falling under the generic name of delayed vibrato attempt to automatically imitate the method in which vibrato is used on orchestral instruments such as the violin. When a key is actuated the vibrato is not applied instantaneously. Instead after a predetermined time delay the vibrato is applied to gradually increase to its full magnitude. Thus for fast passages the vibrato is not applied if each note is released before the time delay threshold has been reached. A delayed vibrato system is disclosed in U.S. Pat. No. 3,951,030 entitled "Implementation Of Delayed Vibrato In A Computor Organ."
With the notable exceptions of the conventional pipe organ and harpsichord, a skilled musician will vary the attack of a note to lend an expressive dimension to the speed of a sequence of notes as well as to some emotional quantity. The attacks are not all uniformly alike with a mechanical-like precision characteristic of pipe organs, harpsichords, and the usual keyboard electronic musical instrument.